The present invention relates generally to corrosion inhibitors for use in reinforced concrete structures, and more particularly to corrosion inhibitors for reducing the rate of corrosion in metallic reinforcing rods placed within structures formed of concrete. The present inhibitor is designed for use in admixture with raw concrete, and hence is provided on an in-situ basis within the concrete mixing.
Concrete structures such as highways and bridges typically utilize metallic reinforcement members embedded therewithin to provide stability and additional strength to the concrete, and to enhance the ability of the concrete to withstand shear forces. These reinforcements are typically in the form of reinforcing rods, wire mesh, metallic fibers, and the like, and are usually situated in regular intervals within the cured concrete by pouring raw or uncured concrete therearound or, in the case of metallic fibers, added during the concrete mixing operation, for subsequent curing. The term "raw concrete" is utilized in a comprehensive sense, and is intended to relate to wet workable concrete mixtures which have not yet cured to their solid form. Upon the passage of time, the metallic reinforcements have a tendency to corrode as external elements such as moisture, atmospheric pollutants such as carbon dioxide, oxides of sulfur, oxides of nitrogen, hydrogen sulfide road treatment chemicals permeate through the concrete structure and reach the metal. When utilized in highways, bridges, and parking structures, chlorides including sodium chloride and calcium chloride may permeate the concrete structure due to the widespread utilization of such materials as a mechanism to melt ice and snow from the road surfaces. Both calcium chloride and sodium chloride are widely used for this purpose.
In order to facilitate the access of inhibitors to concrete reinforcements, including particularly the surfaces of concrete reinforcements, it is desirable that corrosion inhibitors be added to the raw concrete mixture in order to provide for contact with the surfaces of the metallic reinforcement members or structures. The corrosion inhibitor added in this fashion normally migrates at a rate sufficient to provide ongoing protection over relatively extended periods of time, and hence have an ability to protect the metallic reinforcements over such a period of time. It is, of course, always possible to boost the effectiveness of the inhibitor on a post-cure basis, provided the inhibitor can be placed within the body of the concrete.
In accordance with the present invention, a formulation has been developed which is readily adapted for use in admixture with raw or wet concrete mixtures, and which provides long-lasting and reliable corrosion inhibiting properties for metallic reinforcements. The formulation of the present invention facilitates the inhibition of corrosion while, at the same time, not adversely impacting or affecting the curing rate or ultimate strength of the concrete in which it is added.
Therefore, it is a primary object of the present invention to provide an improved in-situ corrosion inhibitor designed for admixture with raw or wet concrete mixtures, in which metallic reinforcements are placed.
It is a further object of the present invention to provide an improved formulation for use in admixture with raw or wet concrete mixtures wherein the formulation provides protection for the metallic reinforcements without adversely affecting the curing rate or ultimate strength of the concrete.
Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification and appended claims.